FORMS PREVIOUSLY DESCRIBED. 53 



RARE FORMS. 



A number of rare forms which were observed on these crystals 

 are entitled to a short discussion. The results are also applied to 

 the tabulation of the forms of the wolframite group as developed on 

 a later page. 



r{120}, already noted by Descloizeaux and Jeremejew, 1 is probably 

 present as a line face on crystal 1; <j> measured 33 49' (calculated 

 31 12'). 



<2{830}, found by Penfield on hubnerite from Colorado, 3 is verified 

 by the presence of two line faces on the crystals herein described. 

 On crystal 18 a line face yielded a fair reflection whose measurement 

 gave (j> a value of 73 06' (calculated 72 48'); crystal 23 showed a 

 very narrow face, the measurement of whose reflection gave $ a 

 value of 73 32' (calculated 72 48'). Penfield's 2 letter q was 

 changed 3 to Q, as q had already been preempted by the form {103}. 



d{310}, noted by Krenner, Boggild, and as doubtfully present 

 by Moses, was found once on crystal 9 as a very narrow face, giving 

 a poor reflection. < measured 74 47' (calculated 74 37'). The 

 occurrence is illustrated in figure 24 (p. 66). 



7*{610} was first described by Boggild, who assigned to the new 

 form the letter p. As this letter had been used by Moses to desig- 

 nate the form {214}, I have changed Boggild's p to j, as here given. 

 The form was noted once, on crystal 9, as a medium-sized striated 

 face; <j> measured about 82 (calculated 82 10') The form is shown 

 in figure 27 (p. 67). 



n{810}, first noted by Groth and Arzruni, has been observed a 

 number of times on these crystals. Some occurrences are shown in 

 figures 22, 25, and 27. The angles measured are as follows: 



Measurements of n { 810 } . 



^{104}, observed only by Jeremejew, is confirmed by finding it on 

 crystal 13 as a line face with 2(102) and 77(904), as shown in figure 25 

 (p. 66). The reflection was very poor and its measurement gave p 

 16 28' (calculated 15 08'). 



See Bibliography, pp. 74-75, for references. 



* Dana's System of mineralogy, 6th ed., p. 982. 



* Goldschmidt's Winkeltabellen, p. 366, 1897. 



